Automatic lock for trailer vacuum brakes



June 17, 1952 A. J. GROSS AUTOMATIC LOCK FOR TRAILER VACUUM BRAKES Filed Nov. 1'7, 1948 Patented June 17, 1952 FFICE AUTOMATIC LOOK FOR TRAILER VACUUM BRAKES Adolph J. Gross, Chicago, Ill.

Application November 17, 1948, Serial No. 60,583

1 Claim. 1

This invention relates to a brake lock that takes the form of an accessory attachment adapted to be used with the conventional brake systems found on various vehicles such as the detachable trailers of truck-trailer units.

The truck-trailer or other vehicle units to which my invention may be applied ordinarily have a vacuum type system that controls the mechanical operation of the brake shoes in relation to the brake drums. This system, in the usual case, depends for operation upon the use of vacuum, or more specifically, the use of two 00- operating vacuums, each of which is derived from the motor in the truck of the truck-trailer unit.

The communicating pipes or conduits that conduct the vacuum generated in the motor of the truck to the point of application at the brake controls of the trailer are herein termed lines. Thus, two lines are present, each with a suitable coupling means at a convenient point so that separation is possible when the trailer is disconnected from the truck, as it often is for loading, unloading, or storage.

As mentioned, the controls for the brakes provided on the trailer vehicle depend for their op eration upon the existence and maintenance of a condition of vacuum in the vacuum lines. Accordingly, when a trailer is disconnected from its associated truck, whether or not its brakes remain in applied condition depends entirely upon the maintenance of a vacuum in its brake control system. In practice, it has been found that the brake control systems are not in fact perfectly air tight, and, as a result, the vacuum is lost.

sometimes after a comparatively long period, and sometimes very quickly after the trailer has been disconnected. After the vacuum has been lost. the brakes relax, and do not thereafter eiiectively act to prevent unwanted movement of the trailer. Consequently, it has become common practice to place blocks on both sides of the various wheels of the trailer.

The object of the present invention is to provide a small, simple, inexpensive and highly satisfactory attachment that may be applied to the braking system of a conventional trailer or other vehicle equipped with a vacuum brake control system, and which will, at the time the trailer is uncoupled from its associated truck, automatically eifect a mechanical locking of the trailer brakes. This mechanical locking of the trailer brakes is entirely independent of the vacuum that otherwise is relied upon to maintain the brakes in applied condition. In other Words, if the vacuum should escape or decrease in value for one reason or another, the mechanical lock of my invention is present to maintain the brakes in applied condition for an unlimited period of time.

With my invention, therefore, the immobility of an uncoupled trailer no longer depends upon the thoughtfulness of the truck driver to place blocks in adequate number and size in front of and behind the wheels of the trailer. My invention is automatic and secure in its operation, and it functions at the instant the vacuum lines to the trailer are uncoupled when the trailer is disconnected from the truck.

Other objects and advantages of my invention will be apparent as the description proceeds, reference being had to the accompanying drawing wherein one form of the invention is shown. It is to be understood that the description and drawing are illustrative only, and are not to be taken as limiting the invention except insofar as it is limited by the claim.

In the drawing:

Fig. 1 is a top view of a conventional vacuum type brake control system and associated brake shoes showing my invention applied thereto;

Fig. 2 is a partly broken away view taken on line 22 of Fig. l; and

Fig. 3 is a view taken on line 3-4 of Fig. 1.

To facilitate explanation of my invention, it'is considered desirable first to describe briefly the conventional vacuum type brake control system with which my invention is normally used. Only one set of brakes, i. e. those associated with a single pair of opposing wheels, and-a single control system, are shown in the drawing, although it is apparent that duplication is possible with other sets of opposing wheels if desired.

A wheel carrying axle of a vehicle is shown at 5, the illustrated axle being for the most part rectangular in cross section. The axle ends 6 are machined to a circular cross section for the reception of wheels and wheel bearings (not shown).

Brake shoes I and 8 (Figs. 1 and 3) are mounted for operation near the ends of axle 5, the re= spective shoes cooperating in the usual manner with brake drums (not shown) carried by the vehicle wheels. Brake shoe 8 has been removed in Fig. 2 for clarity. Power chambers H and I 2 (Fig. 1) are mounted on axle adjacent brake shoes I and 8 respectively. As will be presently seen, each power chamber exercises control over operation of its respective, adjacent brake shoe.

Brake shoes I and 8 expand under the influence of cams l3 and [4, the shape of cam [4 being best shown in Fig. 2. In this figure, the cam is shown in its brake applied position, i. e. the assQciated brake shoe, if it were shown, would be expanded to a maximum ,degree by the cam. Brake shoe 7, in Fig. 2, is correspondingly expanded.

Cam [3 is carried by and rotates with a shaft 5 (Figs. 1 and 3) that is journalledina bearing 56 extending from axle 5. Similarly, cam? 1| 4. ;has a shaft I 9 and associated bearing .20. Camll i (Fig. 2) is actuated by means of an L shaped arm 22 that forms a connecting Ilink between shaft l9 and a connecting rod 23 extending from power chamber I2. A clevis 24 at the end of connecting rod 23 forms a pivotal connection between rod 23..and. the L-shaped arm 22, asbest shown in Figs; 2:and 3. Similarly, shaft [5 has an l -shaped arm126 that'connects through clevis 21 to the connecting rod of power chamber .II for actuation of cam l 3.

l wo lines 30 and 3| (Fig. l)-extend from the truck-motor to a point in-the vehicle adjacent theabove described"brake control apparatus. Each line has. a coupling (not shown) so' that the lines may be broken .when 'the trailer is disconnected from the truck. During operation of the. truck motona condition of vacuum normally -exists in both lines.

Line 30, commonly called' the live line, oom- --municates through short line- 32 and check 'valve 33- with reservoirtank 34. -A substantial vacuum is maintained "at all times during. truck operation in tank 34 by virtue of this connection with line 30. In fact, under idealized conditions the same degree of vacuum is supposed to be maintained in tank 34 also when-the trailer is separated from-thetruck,-and parked for an extended periodof time. However, due to failure to achieve or maintain idealized conditions, the vacuum in tank 34 decreases with time when the trailer is separated from the-truck, that is, when live line 30 is not continually providing vacuum. Check valve 33, ofcourse, 'isprovided -to:prevent-escape of vacuum :throughi'lines' '39 and 32-when the wcouplingiis broken.

Line 3| is called the 'control line,and it leads to a control valve 36. Thevalveifi is disposed between-tank and a pair of diverging lines =3! and 38 that leadrespectively to-power chambers II and I2. Asstated, -a-"vacuum is normally maintained in control line 3|, this vacuum being effective to maintain control valve I 35 in closed condition insofaras communication ghetweentankil-andflines Brand 38 is concerned.

When trailer braking action is desired, as is periodicallymecessary' during normal driving, the truck driver-actuates the brake pedal or other control in the cab of the truck. This action -releases the'vacuum' from control line 5 which *in turn causes valve 36 to open, thus impressing the substantial vacuum contained in tank 34 on the power chambers H and 12. This substantial vacuum causes a retraction of the connecting-rods extending from the respective power 4 chambers so that they tend to assume the withdrawn position as characterized by the position of rod 23 in Fig. 2. Retraction of the connecting rods causes rotation of the respective L- shaped arms 22 and 26 which in turn rotate shafts l9 and I5 and their associated cams l4 and I3, thus to expand brake shoes 8 and l to apply the brakes. When vacuum is again applied to control line 3|, as occurs when the truck driver releases the brake pedal, valve 36 closes to remove the substantial vacuum in tank 34 from the power chambers I! and I2. Thereup n r storin sp ngs- (notshown) contact the brakeshoes, and extend the connecting rods from the respective power chambers. This restores the "control system to a condition for a subsequent *braking operation.

ilfheabovedescribed vacuum type brake control system forms no part of my invention, but, as

state d, it.is here set forth to assist in an understanding of my invention which now will be de- :scribed.

My invention takes the form of an attachment or accessory that may be used in a vehicle having a vacuum type brake control system of the character described. The attachment, in the form illustrated, inc1udes a frame 40 (Fig. 2) having a vertical 'leg' 4 I and a horizontal -leg- 42. Frame 40 is suitably: mounted on axle -'5 -ata point substantially midway between the *axle ends. As shown,horizontal -leg-42-isseated on the'top of axle5. A plate 43"(Fig. 3) provided with bolts 44, one of which isshown in Fig. 3, may beassociated with leg-'42 -so-- as to effect a clamping relationship with axle '5.

"Leg42" has anaperture-near its free end, and in alignment therewith there is provided -atubular bearing 46 (Fig.2). A lockrodAT-is-journalled for longitudinal (up'and down) movement in bearing 46. A spring 48 extends between bearing 4'6-and lock rod. 47 to apply pressure tendingto-keep slack-out of the system, thus to compensate for wear in the various linkages.

Thelower'end '49 of lock rod is provided :with a universalpoint'ifl' (Fig. 3) that connects with a-transverse member 5!. The-member 5| desirably should be constructed so'that its length is capable of variation, and to thatend the member may have end portions-52 and-53 that are :reducedin part to telescopewith -the member. The portions 52:.and 53 are"thusable to slide in and out of'the ends of member 5|, :as often is necessary due to unequal conditions in the "brake systemsuch as uneven wear of the';individual brakes. Also, the distance'between'power chamabers II and I2 .(withwhichthe ends of member 5|.are in vertical alignment) varies among different vehicles. Thus the variable length featureof member 15! makes application of myat- ,tachment .to various vehicles particularly easy. The portions. 62. and 53' also form respective elements of universal jointsthat haveas theirother elements'the clevises 24 and 21 mentioned previously, the clevises being suitably modified to receive portions-52 and 53.

From the-construction cf my'inventionso far described, itwill be-seen-that Ishave provided a transverse member -5| linking-the-opposed clevises 24- and 2l cf the conventional vacuum type brake control system. These clevises, of course, move toand'fro in connection with -normal brake cperation. In so doing they impart in generaladisplacement-type movement to transverse member 35 l. Because of ,uneven brake wear and other factors; the two clevises do 'not always move in a corresponding manner and amount. Accordingly, the need for universal joints at the ends of transverse member and the variable length feature of the member are apparent.

The displacement movement of member 5| is translated through universal joint 50 into vertical up and down movement of lock rod 41 in bearing 46. Thus, when the brakes are applied, as shown in Fig. 2, rod 41 will move to or near its upper limit of movement. Conversely, when the brakes are relaxed, rod 41 will move to or near its lower limit of movement. In other words, rod 4'! fluctuates up and down in response to brake operation.

An auxiliary power chamber 55 is mounted on leg 4| of frame 40. This power chamber is connected by means of line 56 to live line 30, as best shown in Fig. 1. Auxiliary power chamber 55 is of a well known type such as that shown in U. S. Patent No. 2,127,890. The chamber there referred to comprises diaphragm casing 5, diaphragm l, vacuum chamber 8, rod 9 and coil spring IS, the mentioned reference numerals being those applied to Fig. 1 of the drawing forming a part of the said patent.

Power chamber 55 is provided with means for automatically engaging lock rod 41 to maintain the rod in a predetermined position, normally the position shown in Fig. 2 where the brakes are in applied condition. The means here shown includes arm 58, member 59 pivoted to leg 42, and spur 60, all clearly shown in Fig. 2.

Tubular bearing 46 contains a longitudinal opening to provide access of spur 60 to lock rod 4'! so that spur Ell may physically engage the rod.

The location of the pivot for member 59 is so chosen that spur 66 normally extends toward lock rod 4'1 on a bias. This arrangement provides a cam action so that upon engagement of spur 55 with lock rod ll, the tendency of the rod to move in a downward direction tightens the force of engagement between the spur and the rod, thus effectively preventing rod movement in the downward direction. Conversely, tendency of the rod to move upwardly relaxes the pressure of engagement and permits upward motion.

For convenience, member 59 may have an extension providing a handle 62, the handle being useful for relaxing the brake look when the trailer is to be moved without first being coupled to a vacuum system, as when the trailer is moved manually, for example.

A spring 63 surrounds arm 58 between leg 41 and the point of connection between the arm and member 52, the spring tending to move the arm so as to rotate member 55 and its associated spur counter-clockwise from the dotted line position to the full line position shown in Fig. 2. Spring 53, therefore, provides the force that effects initial engagement between spur 60 and lock rod 41, additional force, if necessary, being provided by the tendency of rod 41 to move downwardly as the vacuum in the main vacuum system decreases.

As mentioned, auxiliary power chamber 55 of I my attachment is connected by line 55 to the live line 35 extending from the truck motor. During the time the truck and trailer are connected together and in operation, the vacuum in live line 30 is impressed upon power chamber 55. Under this condition, arm 58 is in its retracted (right hand in Figs. 1 and 2) position, and member 59 and spur 55 are in the dotted line positions (Fig.

2). In other words, auxiliary power chamber'55 holds arm 58 against the force of spring 63.

When the trailer is disconnected from its associated truck, the lines 3| and 30 are, of course, uncoupled. It is immaterial to the effective operation of my invention as to which line is uncoupled first. If line 3| is uncoupled first, the release of vacuum therein causes the brakes to be applied. After the brakes are applied, the various elements in the brake control system assume the positions shown in Fig. 2, with lock rod 4'! of my attachment in its upper position. Thereafter, live line 36 is uncoupled to release the vacuum from auxiliary power chamber 55. Spring 63 then functions to move arm 58 to the left, as shown in Fig. 2, and to rotate member 59 on its pivot. This causes spur 60 to engage lock rod 41 to prevent downward motion of the rod. Since rod 41 is connected by the various linkages above described to the brake cams l3 and I4, the cams are maintained in their brake-applied positions. Under these circumstances, the inevitable escape of vacuum from tank 34 does not adversely affect the applied condition of the brakes.

If live line 35 happens to be uncoupled first. my attachment is actuated so that spur 60 engages back rod 41, thus preventing downward motion of the rod. However, due to the biased spur arrangement, rod 41 is free to move upwardly. Consequently, when control line 3| is later uncoupled, and the main control system functions to apply the brakes, lock rod 41 moves upwardly with the brake applying action. The rod is then retained against downward motion by spur Bil, and the brakes indefinitely remain in applied condition.

When the trailer is again connected to the truck and the lines 30 and 3| are coupled, vacuum is applied to auxiliary power chamber 55 to draw arm 58 to the right. This automatically releases the connection between spur 60 and lock rod 41, and permits the rod to move freely in accordance with the braking action occasioned by normal driving.

From the above description it is thought that the construction and advantages of my invention will be readily apparent to those skilled in the art. Various changes and modifications may be made without departing from the spirit or losing the advantages of the invention.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent is:

A unitary brake lock accessory comprising a frame, a vacuum operated auxiliary power chamber mounted on said frame, said power chamber having a connecting arm, a tubular member mounted on said frame and spaced from said chamber, a lock rod journalled in said tubular member for longitudinal movement, a variable length transverse member having rotatable telescoping ends, a universal joint means connecting the midpoint of said transverse member to one end of said lock rod, a universal joint means, including a rotatable telescoping end, at each end of said transverse member, a lever member pivoted at one end to said frame and disposed between said power chamber and said tubular member, the connecting arm of said power chamber being pivotally attached to said lever member at a point spaced from the pivoted end of said lever member, a spring tending to extend the connecting arm with respect to said chamber, and a cam spur on said lever member between the pivoted end of said lever member and the point of attachment of said connecting x'a rmasaidcamspur engegingjsaid lockzrod'topreventpllongitudinal movement ijshereof in brake rezleasinghdirection when said springextendsrsaid woonneeting --armfollowing release :of vacuum in saidwpower chamber, said eamtspur being in- -o1ined with-respect to said lock rod in a direction 1 110 tighten the-engagement with said lock rod as fihelat-ter tends to move in brake releasing direction.

ADOLPH J. GROSS.

f 8 .pmm,sIA rEs,-PAT NIs "Number Name I ".Date J Marb1e. '-Dec: 8, 1896 xBaker Sept." 9;'1919 Lovejoy Dec.;28, ,1 920 Moser :Ju1y1; 1928 Bond Sept. ":29,-1936 Francoeur Apr; 13; 1937 Searle -7 Nov.'1.6, 1937 Robinson June 21,1938 Sills, Aug.':'23;1938 Shannon --'May 27,1941 firiizterlden Man-"23; 1943 Forker .Aug. 24,- 1943 

